LeetCode – Refresh – Median of Two Sorted Array

O(m + n):

Note:

return rec[1] not rec[0].

 1 class Solution {
 2 public:
 3     double findMedianSortedArrays(int A[], int m, int B[], int n) {
 4         int mid = (m+n)/2 + 1, i = 0, j = 0;
 5         vector<int> rec(2);
 6         while (i + j < mid) {
 7             int tmp1 = INT_MAX, tmp2 = INT_MAX;
 8             rec[0] = rec[1];
 9             if (i < m) {
10                 tmp1 = A[i];
11             }
12             if (j < n) {
13                 tmp2 = B[j];
14             }
15             if (tmp1 < tmp2) {
16                 rec[1] = tmp1;
17                 i++;
18             } else {
19                 rec[1] = tmp2;
20                 j++;
21             }
22         }
23         if ((m+n)%2 =

 1 class Solution {
 2 public:
 3     double findK(int A[], int m, int B[], int n, int k) {
 4         if (m > n) {
 5             return findK(B, n, A, m, k);
 6         }
 7         if (m == 0) {
 8             return B[k-1];
 9         }
10         if (k == 1) {
11             return min(A[0], B[0]);
12         }
13         int ia = min(m, k/2), ib = k - ia;
14         if (A[ia-1] < B[ib-1]) {
15             return findK(A+ia, m-ia, B, n, k-ia);
16         } else if (A[ia-1] > B[ib-1]) {
17             return findK(A, m, B+ib, n-ib, k-ib);
18         }
19         return A[ia-1];
20     }
21     double findMedianSortedArrays(int A[], int m, int B[], int n) {
22         if ((m + n)%2 == 1) {
23             return findK(A, m, B, n, (m+n)/2+1);
24         }
25         return (findK(A, m, B, n, (m+n)/2+1) + findK(A, m, B, n, (m+n)/2))/2;
26     }
27 };

= 1) return double(rec[1]);
24         return double(rec[0]+ rec[1])/2;
25     }
26 };

O(lg(m+n))

Note:

When do the comparison of A[ia-1] and B[ib-1], do not forget to return it.